I would honestly think twice about this- one of the biggest complaints I hear about from guys looking for escorts is women who are too "plastic" glamour model-alike, with photos that look overly photo-shopped. They might like gawping at Jordan, but none of my male friends would want to shag her. They would quite happily have sexy funtimes with Belladonna though, and she doesn't pack much in the boob area. Big boobs really aren't a guarantee of success
How much work you get depends way more on other factors- what hours you work, whether you do incalls or outcalls, whether you're on adultwork only or have your own site (or both), whether that site is listed on punters' forums. Remember that we are in recession; those at the bottom end of the escort market, price wise, will be less hit than the "high class" ladies and even they will have noticed a drop in punters. Another factor is where you are based- a black escort, for example, in London is simply one of hundreds working that city, but in Glasgow she'll be one of a few and thus will stand out more and may be a bit busier as a result. Webcamming can be a good way of earning money when bookings are slow in coming/non-existent, and some of the ladies here have reported clients booking them as an escort after seeing them on webcam so maybe try that if you're strapped for cash?
I'm only a B cup myself, and they haven't been perky and pert since I was 15 and the nipples are huge. I've had a few comments, but no one's gone "Ohmigod your areolas are hideous! Back, foul demon! Back!"
So you have small boobs. What else do you have? An athletic build? Are you tall like a model? Petite like Kylie? What colour are your eyes? Men like boobs, sure, but they like other things too- do you have a blog? A twitter account? If punters get a good feel for what you/your escort alter ego is like, they may book you on the strength of that. Honestly, I would go for temporary (ish) changes- advertising in different places, dyeing my hair, writing a blog, webcamming- first before going for something permanent like a boob job, and I wouldn't recommend something that drastic just for work. If you aren't happy with them then fine, but I would also say that AA cup -> D cup is a HUGE jump, and can end up looking stuck on and fake (surgeons tend to ask you to put on weight so that your Ds look more natural). Also, you'll have to get them replaced every 10 years, which you'll have to pay for, and if it goes wrong you'll have to pay to correct that too.
To summarise: don't if you're only doing it to get work, but if your boobs make you miserable then go ahead.